Call of Duty: Modern Warfare 3 picks up where Modern Warfare 2 left off with the invasion of Manhattan by Russian forces. You will blaze through 20 action-packed missions located in England, Russia, America, Germany, and France, playing as a Russian Federal Protective Services agent, an SAS Operative and a tank gunner. The Spec-Ops missions from MW2 will make a return, split into "Mission" and "Survival" modes. Also, Call of Duty: MW3 will have the amazing CoD-style multiplayer that you have come to known.
This is basically a stand alone DLC for $60. Lets look at a DLC for Fallout 3. It adds new weapons, a new map/location, and continues/ makes a new story. That is exactly what Modern Warfare 3 does, it adds new maps, new guns and equipment, and continues the story, except Infinty Ward decided to call it a brand new "game". I give it a 2 cause I like the story.